Polyhydridosilanes and their conversion to pyropolymers

ABSTRACT

A polyhydridosilane has a catenated silicon backbone of 9 to 4000 silicon atoms with an average number of hydrogen atoms per silicon atom in the range of 0.3 to 2.2, at least 0.1 gram of the polyhydridosilane being soluble at 20° C. in 100 grams of tetrahydrofuran, toluene, or methylene chloride. The polyhydridosilane can be derivatized or it can be converted to a pyropolymer or a nitrogen-containing pyropolymer which is useful as an abrasive, ceramic, electrical, or electro-optical material.

This is a continuation of application Ser. No. 729,365 filed May 1,1985, now U.S. Pat. No. 4,611,035, which is a divisional application ofapplication Ser. No. 597,540, filed Apr. 6, 1984, now U.S. Pat. No.4,537,942, which is a continuation-in-part of Ser. No. 579,017, filedFeb. 10, 1984, now abandoned.

FIELD OF THE INVENTION

The present invention relates to polyhydridosilanes having catenatedsilicon backbones, certain derivatives thereof, their conversion topyropolymers, and methods therefor. The pyropolymers are useful, forexample, as abrasives, ceramics, and electrical or electro-opticalmaterials.

BACKGROUND ART

The unique properties which characterize organic compounds are due notsolely to carbon atoms, but rather to the bonding of carbon atoms toeach other and to the combination of carbon and hydrogen atoms. Silicon,in the same group of the periodic table as carbon, shares some of thebonding characteristics of carbon and forms analogous catenatedstructures but has its own unique qualities, namely, generally greaterchemical reactivity, and has been the subject of extensive research inrecent years.

Catenated silicon systems are known and are reviewed by R. West in G.Wilkinson, F. G. A. Stone, and E. W. Abel, "Comprehensive OrganometallicChemistry", Volume 2, Chapter 9.4, pages 365-387, Pergamon Press, NewYork (1982). The silicon-silicon bonds in such systems are most oftenformed from two silicon-halogen bonds with a Periodic Groups IA or GroupIIA metal. Generally, groups such as alkyl, halogen, alkoxy, or aryl arepredominantly attached to the catenated silicon backbone.

In contrast to the reported progress in the field of organo-substitutedpolysilanes, the syntheses of the silicon analogs of the parent carbonpolymers such as polyethylene or polypropylene have remained moreelusive. These polymers are classed as silicon hydrides, referred to inthis patent application as polyhydridosilanes, and are generallyreactive towards the atmosphere and not amenable to preparation andstudy without manipulation using vacuum line and/or controlledatmosphere (dry box) techniques.

A few examples of catenated silicon systems containing hydrogen atomsattached to a silicon backbone are known: cyclic polysilanes --SiH₂--_(n) where n=5,6 have been made in multistep syntheses by E. Henggeand G. Bauer, Angew. Chem. Intl. Ed. Eng., 12 (1973), 316 and E. Henggeand D. Kovar, Angew. Chem. Intl. Ed. Eng., 16 (1977), 403; mixtures oflinear and branched polysilanes H--SiH₂ --_(n) H where n=2 to 8 havebeen made by the hydrolytic decomposition of magnesium silicide by K.Borer and C. S. G. Phillips, Proc. Chem. Soc., 189, (1959). Coupling ofalkylhalohydridosilanes with metals to yield Si--Si bonds from systemscontaining Si--H and Si--Cl bonds and related reactions are reviewed byM. Kumada and K. Tamao in F. G. A. Stone and R. West "Advances inOrganometallic Chemistry", Volume 6, pp. 34-36, Academic Press, N.Y.(1968) and disclosed in U.S. Pat. No. 4,276,424.

Insoluble polysilanes have been disclosed. Aromatic silane polymers,formed in radio-frequency plasmas, and which are resistant to hightemperature, adherent to substrates, and electrically insulating aredisclosed in U.S. Pat. No. 4,397,722. Insoluble orange powders havingthe approximate composition --SiH_(n) --_(x) where n is 1 or 2 and x islarge are taught in UK Patent Application No. GB 2,077,710A. As is knownin the art, a substantial degree of crosslinking will render a polymerinsoluble (see Schultz, A. R., Encyclopedia of Polymer Science andTechnology, 4, 336, John Wiley & Sons, NY (1966)).

Silyl derivatives of Periodic Group IA or IIA metals can be formed fromsilicon-halogen, silicon alkoxy, silicon-hydride or silicon-siliconbonds, as described in C. Eaborn, "Organosilicon Compounds", Chapter 12,pp. 357-360, Academic Press, New York (1960). Reaction of catenatedsilicon systems with alkali metals to give delocalized radical anionshas been reviewed by R. West in "Comprehensive OrganometallicChemistry", supra, pp. 393-395.

In the thermal treatment of polymers wherein crosslinking occurs, theresultant materials become stabilized due to the formation of a rigidinsoluble network and the stable products are referred to aspyropolymers by S. D. Bruck and P. F. Liao (J. Polymer Sci., Part A-1,8, 771 (1970)). Pyropolymers have also been described as materials thathave intermediate properties between polymer and carbon by G. M. Jenkinsand K. Kawamura, "Polymeric Carbons--Carbon Fibre, Glass and Char", p.1, Cambridge University Press, London, England (1976).

Formation of elemental silicon by the energetic decomposition of gaseousmolecules containing hydrogen and/or halogen and from one to about threesilicon atoms is well known and is taught, for example, in U.S. Pat.Nos. 4,363,828 and 4,202,928.

Polymeric precursors to elemental silicon are less well known, althoughperhalopolysilanes are mentioned as precursors in U.S. Pat. Nos.4,374,182 and 4,138,509. The formation of silicon carbide (as fibers,films, binders, bulk material and the like) by the energetic treatmentof polymeric organosilanes is disclosed, for example, in U.S. Pat. Nos.4,310,482 and 4,283,376. As U.S. Pat. No. 4,289,720 discloses,multivalent elements such as boron, carbon, nitrogen, oxygen andtransition metals and the like, which are incorporated into thesilicon-containing polymer, are in general also found in thepyropolymer. Alternatively, such multivalent elements can beincorporated into the final pyropolymer by introducing them subsequentto formation of the initial polysilane (such as during pyrolysis). Forexample, decomposition of halogenated silanes in the presence ofnitrogen sources such as ammonia, nitrogen, or their mixtures to formsilicon nitride is reported in assignee's copending U.S. patentapplication Ser. No. 508,852, filed Jun. 29, 1983, now U.S. Pat. No.4,505,720. U.S. Pat. No. 4,393,097 describes a similar amorphoussilicon-nitrogen-carbon composition formed by chemical vapor deposition.U.S. Pat. No. 4,387,080 describes the heating of a mixture containingsilicon, organic silicon polymer, and flaky beta-silicon carbide withgaseous ammonia to give a silicon nitride-containing silicon carbide.

SUMMARY OF THE INVENTION

Briefly, the present invention provides soluble polyhydridosilaneshaving catenated silicon backbones of 9 to 4000, preferably 12 to 4000,silicon atoms with an average number of hydride (hydrogen) atoms persilicon atom in the range of 0.3 to 2.2. In view of the known highreactivity of hydridosilanes towards air, oxygen, water, and inparticular to Periodic Groups IA and IIA metals, it is surprising thatthe polyhydridosilanes obtained by the method of the present inventionare tractable materials which are solids at room temperature andpressure and have the desirable property of being soluble in organicsolvents. The polyhydridosilanes can have use as elastomers, films,fibers, coatings, in composites or articles having utility such asphotoresists, adhesives, or surface modifiers.

In another aspect, the chemistry of the Si-H bond in these polymers canbe exploited e.g., reaction across a carbon-to-carbon multiple bond, orreaction with alcohols, amines, or organometallic reagents, to givemodified or crosslinked materials having use as molding compositions,photoresists, and precursors to ceramic materials.

In a further aspect, polymers containing silyl derivatives of PeriodicGroups IA or IIA metals can be obtained either directly or by treatmentof the isolated polyhydridosilanes with Periodic Groups IA or IIAmetals. These are red, air-sensitive materials which are soluble inorganic solvents, and which demonstrate chemistry typical of silylderivatives of Periodic Groups IA or IIA metals. This reactivity, e.g.with amines, alcohols, thio groups, or carbon-to-halogen or transitionmetal-to-halogen bonds, can be used to give modified materials havingutility as molding compositions, photoresists, and precursors to ceramicmaterials.

In a still further aspect, thermal treatment of the polyhydridosilanesof the present invention provides pyropolymers containing elementalsilicon, silicon carbide, and/or carbon in either combined or elementalform and which are high temperature-stable materials. In yet a furtheraspect, the polyhydridosilane or the pyropolymer can be caused to reactwith a nitrogen source such as gaseous nitrogen or ammonia at elevatedtemperatures to form a new pyropolymer which additionally containssilicon nitride or Si-N bonds.

In the process of the invention, at least one hydridosilane ispolymerized to form a polyhydridosilane wherein each silicon atom in thepolymer preferably has at most one R group and 0 to 2 hydrogen atoms andis connected to 2 or 3 other Si atoms such that a valency of four foreach silicon atom is maintained and such that the average number ofhydrogen atoms per silicon is in the range of 0.3 to 2.2. R can be ahydrogen atom or an aliphatic or aromatic group having up to 25 carbonatoms. A mixture of hydridosilanes can be copolymerized to givepolyhydridosilanes having aliphatic, aromatic, or a combination ofaliphatic and aromatic groups in addition to hydride in the resultantpolymer, or a hydridosilane can be copolymerized with silanes containingno hydride. The process of the invention provides organicsolvent-soluble catenated silicon systems containing silicon-hydrogenbonds which can be prepared from silanes in a one-step process. In theprior art, tractable polysilanes were prepared from silanes, but theresultant polysilanes did not contain silicon-hydrogen bonds, unlessthey were introduced in subsequent steps. Further, it is believed thattractable polyhydridosilanes having at least 9 catenated silicon atomsand an average in the range of 0.3 to 2.2 hydrogen atoms per siliconatom are novel.

Pyrolysis of the resulting polyhydridosilanes of the invention provides(1) pyropolymers containing elemental silicon which can be useful inelectronic and electrooptical applications, (2) pyropolymers containingsilicon and silicon carbide which can be useful in electronic, ceramic,and other applications, and (3) pyropolymers containing silicon carbidewhich can be useful in ceramics and photovoltaics. Further, pyrolysis inthe presence of a nitrogen source results in silicon nitride-containingpyropolymers which may be used as abrasives and ceramics.

In the present invention:

"catenated" means a joined silicon-silicon backbone which can be linear,branched, cyclic, or combinations thereof, and the valence of eachsilicon atom is four;

"oligomer" means a compound containing 2, 3, or 4 monomer units;

"polymer" means a compound containing more than 4 monomer units;

"film-forming" means sufficiently soluble in a common volatile organicsolvent such as toluene, tetrahydrofuran, or dichloromethane to enable acoating to be deposited by conventional coating techniques such as knifecoating or bar coating; generally, a solubility of polyhydridosilane aslow as 0.1 gram in 100 grams of organic solvent at 20° C. is useful,although a solubility of at least 1 gram is preferred;

"silicon hydride" or "hydride" means a hydrogen atom which is bondeddirectly to a silicon atom;

"silyl derivative of Periodic Groups IA and IIA" means a compoundcontaining a silicon atom bonded to three groups preferably selectedfrom hydrogen, aliphatic or aromatic group, or another silicon atom andcontaining a silicon-to-metal bond where the metal is a Periodic GroupIA or IIA metal;

"silane" means a compound having the formula SiA₁ A₂ A₃ A₄ where each ofA₁ to A₄ may be chosen from alkyl, alkenyl, aryl, halogen, alkoxy,hydrogen or other radicals such as amino, cyano, and mercapto;

"hydridosilane" refers to a silane where at least one of A₁ to A₄ ishydrogen;

"polysilane" means a polymer containing a catenated silicon backbonewith other atoms or groups pendant such as hydrogen, halogen, silicon,organic groups (optionally including hetero atoms), Periodic Group IA orIIA metals, or inorgano- or organometallic groups, such that eachsilicon maintains a valency of 4;

"polyhydridosilane" means polymers resulting from polymerization of atleast one hydridosilane and having catenated backbones with an averagenumber of hydride atoms per silicon atom in the range of 0.3 to 2.2;

"single bond connecting two silicon atoms" means that a single bondattaches a catenated silicon atom of one polymeric backbone to a siliconatom which may be on another polymeric backbone so as to effect abranch-point, crosslink, or cyclic structure in the resulting polymericchain;

"substantially crosslinked" means a three-dimensional polymeric networkwherein the resultant polymer is no longer soluble;

"soluble" means that a finite amount of a compound can be dissolved in aparticular solvent to give a solution; i.e., the solution contains atleast 0.1 gram of polyhydridosilane, and preferably 1.0 gram, dissolvedin 100 grams of organic solvent such as tetrahydrofuran, toluene,methylene chloride, etc. at 20° C., or in the case of a dispersion itwill pass through a 10 to 15 micrometer fritted glass filter medium;

"tractable" means having properties such as solubility, volatilityand/or extrudability to an extent that allows study and processing;

"pyropolymer" means a stable polymer produced by thermal treatment ofpolymers wherein crosslinking occurs;

"catenary" means in the backbone, not a terminal or pendent group;

"elemental carbon" means any of the allotropic forms of carbon; and"organometallic group" means a group containing carbon to metal bond.

DETAILED DESCRIPTION

The present invention comprises a polymer having a backbone comprisingrepeating monomeric units having the formula: ##STR1## wherein all R'smay be the same or different and are independently selected from thegroup consisting of (1) hydrogen, (2) a linear, branched, or cyclicaliphatic group (preferably alkyl or alkenyl) having 1 to 10 carbonatoms and optionally containing at least one Periodic Group VA or VIAatom which is preferably selected from oxygen and nitrogen, (3) anaromatic group [preferably aryl, aralkyl, or alkaryl group (wherein arylpreferably is a single ring, such as phenyl, benzyl, tolyl, or a fusedring, such as naphthyl)], all of these groups optionally substituted byup to three C₁ to C₁₀ linear, branched, or cyclic aliphatic groups, saidaromatic or aliphatic groups optionally containing at least one PeriodicGroup VA or VIA atom which preferably is selected from oxygen andnitrogen, the total number of carbon atoms being up to 25, (4) a singlebond connecting two silicon atoms, (5) a metal atom selected from thegroup consisting of Periodic Groups IA and IIA, and (6) an inorgano- ororganometallic group comprising at least one Periodic Group IB to VIIB,VIII, and Lanthanide and Actinide element;

wherein the ratio of hydride to silicon is in the range of 0.3 to 2.2;and the average number of monomeric units in the polymer is in the rangeof 9 to 4000, preferably 12 to 4000.

R can be an aliphatic or aromatic group capable of forming one or morebonds to one or more silicon atoms which group optionally can contain atleast one atom of N, P, As, Sb, Bi, O, S, Se, and Te. These heteroatomsmay or may not be bonded directly to a silicon atom which is part of acatenated system, e.g., alkoxy such as --OCH₃, arylalkylamino such as--N(CH₃)(C₆ H₅ CH₂), ether (catenary oxygen) such as --(CH₂)₂ --O--CH₃,arylthio such as --S(C₆ H₅), and alkylphosphino such as --P(C₂ H₅)₂.Preferred R groups include hydrogen, methyl, ethyl, n-butyl, methoxy,phenyl, benzyl, benzylmethylamino, phenethyl, silicon, lithium, sodium,and iron (dicarbonyl)cyclopentadienyl.

The polymers of the invention, wherein the monomeric units may berandomly arranged, are film-forming and soluble in common organicsolvents, have catenated silicon backbones, and are commonly referred toas polyhydridosilanes. They are also referred to in the art aspolysilylenes and polysilanes. Polyhydridosilanes may have utility asprecursors to pyropolymers. The polyhydridosilanes can be coated asfilms, drawn into fibers, or utilized in bulk or as binders beforepyrolysis.

Polyhydridosilanes of formula I, wherein n has an average value in therange of 9 to 4000, preferably 12 to 4,000, more preferably 20 to 2000,and most preferably 30 to 1000, have average molecular weights in therange of 350 to 500,000. Lower molecular weight polyhydridosilanes,i.e., where n has an average value of 9 to about 15, are liquids withhigh vapor pressures. They are more difficult to handle in air (i.e.,they readily oxidize) than higher molecular weight polyhydridosilanesbut they may be preferred in applications where appreciable volatilityis desirable.

Hydridosilane monomers alone or in the presence of organosilanespolymerize in the method of the invention in one step topolyhydridosilanes. Polyhydridosilanes can be prepared by

1. providing a suitable hydridosilane having the general structureH(R¹)SiX₂, where R¹ is as defined above for R groups (1) to (4), exceptthat R¹ groups chosen from R groups (2) to (4) must be sufficientlystable so as to be unreactive under the conditions of the reaction(preferably only catenary oxygen is present as a heteroatom), andwherein the hydridosilane preferably contains at most one aliphatic oraromatic group per silicon atom, and X is a halogen atom, preferablychlorine, and

2. reacting the hydridosilane above with a suitable periodic Group IA(alkali) or Group IIA (alkaline earth) metal or alloy in an amount of atleast 1 equivalent of metal per equivalent of halogen in an inertatmosphere such as argon or nitrogen and in an inert diluent such astetrahydrofuran or toluene for a period of time sufficient to providethe desired polyhydridosilane.

Preparation of polyhydridosilanes according to the present invention maybe illustrated by the following equation (1) (for a Group IA metal)##STR2## where R¹ is as defined above, and M is a Periodic Group IA orGroup IIA metal or alloy. X is preferably chlorine but may be anotherhalogen such as bromine or iodine or a combination of halogens. Themonomeric units shown in equation 1 are repeating and may be randomlyarranged in any proportion. There are from 9 to 4000 monomeric units ineach polymer. The silicon-hydride bonds are not completely inert to thereaction conditions, and some of them react to form Si--Si bonds, with ahydride to silicon ratio in the range of 0.3 to 2.2. The positions alongthe catenated silicon backbone where the hydride has reacted containsilicon atoms bonded to three or four other silicons, so that a valencyof four is maintained and may be branch points, parts of a cyclicstructure or crosslinks. When one R¹ is selected from aliphatic oraromatic groups the R¹ --Si bond is inert to the reaction conditions,and thus each silicon in the polymer will be bonded to two or threeother silicons, one R¹ and zero or one H. When one R¹ is hydrogen, theR¹ --Si bond is no longer inert to the reaction conditions, and eachsilicon atom may now be bonded to two, three or four other silicon atomsand two, one or no H atoms, such that a valency of four is maintainedfor each silicon atom.

Examples of hydridosilanes H(R¹)Six₂ which may be used as startingmaterials in the present invention include methyldichlorosilane,ethyldichlorosilane, phenyldichlorosilane, dichlorosilane, and the like.The invention is not intended to be limited to these particular startingmaterial silanes.

The polymers of the invention are soluble in organic solvents such astetrahydrofuran, toluene, methylene chloride and the like, formingsolutions of at least 0.1 gram in 100 grams of organic solvent andpreferably 1.0 gram per 100 grams of solvent. Many of the polymers areeven more soluble than that, and solutions of 10 grams or more per 100grams of organic solvent can be obtained. This distinguishes them frommaterials of similar composition in the prior art, in that thosematerials are insoluble. Solubility is a desirable property, in that itallows convenient study and handling of these materials. Those skilledin the art will appreciate that this property can allow the polymers tobe cast into films and fibers, further modified chemically inhomogeneous reactions, conveniently analyzed, or otherwise manipulatedor formed.

The polyhydridosilanes of the invention are white or pale yellow, andmay be transparent or translucent or opaque. They may be air-sensitiveor stable in air, depending on the substituents R; generally,electron-with-drawing groups R yield a material which is more air-stablethan those materials with electron-donating groups.

Copolymers of hydridosilanes can be prepared by the reaction of amixture of different hydridosilanes with a suitable metal. For example,an aliphatic-substituted hydridosilane with an aromatic-substitutedhydridosilane can be caused to react with a metal such as sodium toyield a random copolymer comprised of randomly repeating units of analkyl-substituted hydridosilane with randomly repeating units of anaryl-substituted hydridosilane. This reaction may be exemplified by thegeneral equation ##STR3## where R¹ and R² may be the same or differentand are independently selected from R groups (1), (2), (3), and (4), andM, and X all are as defined and restricted above, and R¹ and R² are notall alike. The monomeric units shown in equation 2 may be randomlyarranged, and there are from 9 to 4000 monomeric units in each polymer.As was described above, the Si-H bonds are not inert to the reactionconditions, and the polymer contains a hydride to silicon ratio of from0.3 to 2.2, with a valency of four being maintained for each siliconatom. Hydridosilanes may also be copolymerized in a similar manner withsilanes containing no hydrogen on the silicon atoms. The metal withwhich the hydridosilane is treated may be a Group IA metal such aslithium, sodium, potassium or alloys or combinations thereof or a GroupIIA metal such as magnesium which will reduce silicon-halogen bonds. Atleast one metal equivalent per equivalent of halide is used. Atemperature in the range of -78° to 150° C. can be utilized. Otherreducing conditions and techniques, such as electrolysis, are alsosuitable. Reaction times are sufficient, depending on temperature, toallow the silicon-halogen bonds to react and form the polyhydridosilane.

Equations 1 and 2 are intended only as examples, and it is not intendedthat the invention be limited to these particular combinations.

Reactions of the present invention can proceed readily under mildconditions (i.e., -78° to 40° C.) without the necessity of usingelevated temperatures. As with any reaction involving the use of alkalimetals and/or silicon halides, the reaction is performed under anhydrousconditions in the absence of reactive oxygen in an inert atmosphere,such as nitrogen or argon.

The reaction may be carried out in any suitable solvent or vehicle whichdoes not adversely affect the reactants or products, and tetrahydrofuranas solvent is particularly suitable. Other solvents which are suitableand in which the resultant colorless or lightly coloredpolyhydridosilanes are soluble are 1,2-dimethoxyethane (glyme), andtoluene.

Useful catalysts to increase the rate of reaction of hydridosilanes withthe previously mentioned metals include naphthalene and otherpolynuclear aromatics. In the case where a dihydridosilane is used,naphthalene as catalyst is particularly desirable because it allows thereaction to proceed under very controlled conditions (i.e., temperaturesin the range of -78° to -40° C.) which avoids formation of a substantialnumber of crosslinks and the production of insoluble materials. Astoichiometric amount of catalyst can be used, but preferably an amountin the range of 0.01 to 5.0 mole percent per hydrosilane compound andmost preferably 0.1 to 1.0 mole percent is employed.

Upon mixing of a hydridosilane and a Periodic Group IA or IIA metal, orcombinations or alloys thereof, an exotherm is observed. The resultingpolyhydridosilanes, which are the precursors to the pyropolymers of theinvention, can then be isolated and stored as long as they are kept freefrom moisture and oxygen, i.e., they are kept in an inert atmosphere inthe absence of light at 25° C. or less. The polyhydridosilanes aresoluble in common organic solvents such as toluene, tetrahydrofuran,glyme, and dichloromethane.

In another aspect of the invention, silyl derivatives of Periodic GroupsIA and Group IIA metals may be formed from Si--X (where X=halogen),Si--H, Si--Si or catenated silicon systems by several mechanisms. Underappropriate reaction conditions (preferably, sufficient reaction time inthe presence of a sufficient quantity of Periodic Groups IA or IIA metalM, preferably sodium, potassium, lithium, or magnesium), a polymercontaining silyl derivatives of metals M may be obtained in a one-stepsynthesis using more than 1 equivalent of metal per equivalent ofhalogen. Alternatively, one can allow polyhydridosilanes of formula I toreact with M metals in an amount of 0.01 to 5 equivalents of metal perequivalent of hydride in an appropriate solvent under inert atmosphereand obtain silyl derivatives of the metal in this manner. Materialsprepared by either method demonstrate the reactivity expected of silyl-Mcompounds such as reaction with an aliphatic or aromatic halide or atransition metal halide complex:

    (R.sup.1).sub.3 Si.sup.- M.sup.+ +R.sub.3 C--X→(R.sup.1).sub.3 Si--CR.sub.3 +MX                                          (3)

    (R.sup.1).sub.3 Si.sup.- M.sup.+ +TX.sub.n L.sub.m →(R.sup.1).sub.3 Si--TX.sub.(n-1) L.sub.m +MX                              (4)

    (R.sup.1).sub.3 Si.sup.- M.sup.+ +CuCl→(R.sup.1).sub.3 Si--Si(R.sup.1).sub.3 +Cu+MCl                             (5)

where R, R¹, M and X are as defined above. A transition metal halidecomplex is represented by TX_(n) L_(m) where T can be selected from oneor more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh,Ir, Ni, Pd, Pt, or Actinide or Lanthanide metal, X can be a halogen (Cl,Br, or I), n can be an integer from one to five; L can be independentlyselected from one or more of the following groups: (1) an aliphatic oraromatic group containing one or more carbon-to-carbon multiple bondssuch as ethylene, diphenylacetylene, benzene, cyclooctadiene,cyclopentadienyl, and toluene; (2) a group containing one or morePeriodic Group VA atoms optionally substituted with up to 4 groupsindependently selected from aliphatic and aromatic, and a hydrogen atom,such as ammonia, trimethylamine, triphenylphosphine, trimethylphosphine,dimethylphenylphosphine, tetramethylammonium, triphenylarsine, and1,2-bis(diphenylphosphino)ethane; or the Group VA atom or atoms may bepart of an aromatic group, such as pyridine or 2,2'-bipyridyl, or theGroup VA atom may be multiply bonded to carbon and optionallysubstituted with at least one aliphatic or aromatic group, such ascyano, acetonitrile, or t-butylisocyanide; (3) a group containing one ormore Group VIA atoms optionally substituted by up to 5 groupsindependently selected from aliphatic and aromatic groups, or a hydrogenatom, such as tetrahydrofuran (THF) or, the Group VIA atom(s) may bemultiply bonded to carbon and optionally substituted with at least onealiphatic or aromatic group, such as acetylacetonate,(4) R¹, where R¹ isas defined above, such as CH₃, t-butyl, or phenyl (5) CO; and wherein mis selected depending on L so as to achieve a stable compound,generally, an 18 electron configuration, or for metals such as Rh, Ir,Ni, Pd, and Pt, a 16 electron configuration may be stable. Generally, mcan be an integer in the range of 1 to 6.

Examples of stable inorgano- and organometallic compounds are:

(1) (Cp)₂ TX₂, where T can be Ti, Zr, Hf; X can be Cl or Br; andCp=cyclopentadienyl;

(2) CpT(CO)_(p) X, where T can be Cr, Mo, W, where p=3, and X can be Clor Br; or T can be Fe, Ru, Os, where p=2, and X can be Cl or Br;

(3) [(R¹)₃ P]₂ TX₂ or [(R¹)₃ P]₂ TX(R¹), where where T can be Ni, Pd,Pt, and X can be Cl, Br, or I;

(4) CpT(CO)X₂ or CpT(CO)X(R¹) where T can be Co or Rh; X can be Cl;

(5) [C₅ (CH₃)₁₀ ]₂ TX, where T can be Lu or Y;

(6) (NH₃)₂ PtCl₂ ; (CO)_(q) TX, where T can be Co, Rh, or Ir; q=4 and Xcan be Cl or Br; or where T can be Mn or Re, q=5, and X can be Cl or Br;(Co)_(r) TX₂, where T can be Fe, Ru, Os, r=4, and X can be Cl or Br.

Other suitable compounds may be found in many reference on inorgano- ororganometallic chemistry. In Equations 3, 4 and 5 above, one or more ofR is a single bond connecting two silicon atoms, so that R₃ Si⁻ Na⁺represents part of the polyhydridosilane-containing silyl derivative ofPeriodic Groups IA or IIA.

The polyhydridosilanes derivatized with Periodic Groups IA or IIA metalsremain reactive for long periods of time, so long as they are protectedfrom moisture or other reagents, that is, as long as they are storedunder inert atmosphere. Monomeric units, for example, having the formula##STR4## wherein R¹ and M are as defined above, are present in thepolymer and under appropriate conditions remain active and have thecapability of reacting with groups such as alkyl halides, transitionmetal halides, or an oxidizing agent such as copper (I) chloride. It isnot intended that the invention be limited to these particular examplesof silyl-M reactivity.

In a further aspect of the invention, the Si-H bond in thepolyhydridosilanes described by formula I may be further reacted withreagents other than Periodic Groups IA or IIA metals. The followingexamples illustrate this reactivity:

polyhydridosilane with an alcohol:

    (R.sup.1).sub.3 Si--H+ROH→(R.sup.1).sub.3 SiOR+H.sub.2 ( 6)

polyhydridosilane with an amine:

    (R.sup.1).sub.3 Si--H+R.sub.2 NH→(R.sup.1).sub.3 Si--NR.sub.2 +H.sub.2                                                  ( 7)

polyhydridosilane with an alkene: ##STR5##

polyhydridosilane with an inorgano- or organometallic Periodic Group IAor IIA compound:

    (R.sup.1).sub.3 Si--Si(R.sup.1).sub.3 +M--R.sup.2 →(R.sup.1).sub.2 (R.sup.2)Si--Si(R.sup.1).sub.3 +(R.sup.1).sub.3 Si.sup.- M.sup.+( 11)

In equations 6, 7, 8, 9, 10 and 11, R, R¹, R², and M are as definedabove (and chosen so that (R¹)₃ Si--H represents part of thepolyhydridosilane). In equations 9 and 10, at least one of R is chosenso that R₂ C═CR₂ represents a polyfunctional compound such asdivinylbenzene. Other polyfunctional compounds containing groupsselected from alcohols, amines, and alkenes, such as ethylene glycol,ethylenediamine, ethanolamine, and diallylamine, are also suitable forforming substantially crosslinked networks.

The polyhydridosilanes and derivatives thereof of the present inventionmay contain a variety of reactive sites, such as Si--H bonds, Si--Sibonds and Si--R bonds (depending on R), and others (for example, whenR=alkenyl). Those skilled in the art will realize that under certainreaction conditions, the polyhydridosilanes may demonstrate more thanone type of reactivity, that is, that two or more reactions may occur atdifferent reactive sites under a certain set of conditions. Suchmultiple reactivity may be represented, for example, in Equations 10 and11 (where the proportions of each of the several reactions may vary).Multiple reactivity may be desirable in certain applications.

These examples are meant to serve as illustration only, and theinvention is not intended to be limited to these particular reactions ofSi--H bonds.

In accordance with the present invention, pyrolysis of thepolyhydridosilanes of formula I above, or their derivatives as disclosedabove, preferably in a vacuum or in an inert atmosphere, yieldspyropolymers, which, depending on the composition of thepolyhydridosilane and on pyrolysis conditions, contain at least one ofsilicon, silicon carbide, or carbon. Other multivalent elements, such astransition metals, oxygen and nitrogen, may be incorporated by selectinga suitably derivatized polyhydridosilane. Varying the pyrolysisconditions also results in variation in the molecular weight of thepyropolymers due to changes in crosslinking. Pyrolysis conditionsdetermine, to some extent, the degree of crystallinity of the resultingpyropolymer.

In another aspect of the present invention the polyhydridosilane orpyropolymer may be pyrolyzed in the presence of a gaseous nitrogensource, such as ammonia, and under appropriate conditions siliconnitride may result.

Pyrolysis of the aforementioned polyhydridosilanes is conducted over atemperature range of 200 to 2000° C., preferably 600 to 1600° C., in aninert atmosphere such as argon or in a vacuum until the pyropolymerhaving the desired properties is formed. If it is desired to prepare asilicon nitride-containing pyropolymer, a nitrogen source, such asgaseous ammonia, nitrogen, hydrazine, methylamine, or ammonium halide issubsequently introduced over a temperature range of 700°-2000° C. Ifmore crystallinity is desired, higher pyrolysis temperatures and longertimes are utilized.

Generally, pyrolysis is not observed below 200° C. and a practical uppertemperature is 1600° C. Above 1200° C., morphological changes to themore crystalline forms of silicon, silicon carbide, silicon nitride, andcarbon (graphite) can be anticipated.

The physical and chemical character of the pyropolymer obtained isdependent upon the form and composition of the polyhydridosilane orcopolymeric polyhydridosilane, the temperature of pyrolysis, and whethera gaseous nitrogen source is used during pyrolysis. Polyhydridosilanesas films, fibers, bulk samples, and articles can be pyrolyzed to preparepyropolymers which can be films, fibers, bulk samples or articles. TheSi/H ratio increases with increasing temperature.

Pyropolymers find use, depending on their composition, in a variety ofapplications. Silicon carbide-containing pyropolymers, for example, areused as ceramic materials and as abrasives, and silicon-containingpyropolymers find use as photoconductive materials. Siliconnitride-containing pyropolymers are useful as abrasives and structuralceramics. Other uses of pyropolymers may be apparent to those skilled inthe art and are not limited to those uses stated herein.

As mentioned above, the polyhydridosilanes of the invention (prior topyrolysis) are useful as films, fibers, or articles in applications suchas photoresists, coatings, and composites for modification of surfaces,as elastomers or adhesives, as well as precursors for pyropolymers.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. In all caseseach silicon atom has a valency of four. Where a hydrogen, an aliphatic,or an aromatic group or other group is not indicated, the valency iscompleted by bonding to one or more other silicon atom or atoms, asrequired.

EXAMPLE 1

This example illustrates the preparation of poly(phenylhydridosilane).The entire preparation was conducted in an inert atmosphere of nitrogenunless indicated otherwise.

To seven grams of a magnetically stirred mixture of mineral oil-freesodium dispersion (from Alfa Products, Ventron Division of ThiokolCorp., Danvers, MA) washed free of mineral oil with dry, oxygen-freehexanes in a nitrogen atmosphere, and covered with 150 ml of dry,oxygen-free tetrahydrofuran (THF), 20 ml of phenyldichlorosilane(Petrarch Systems, Inc., Bristol, PA) (the silane was vacuum-distilledbefore use) was added dropwise over 1.5 hrs. at ambient temperature(about 20° C.). The product was stirred for three days and the resultantred mixture was filtered to remove excess sodium dispersion and NaCl. Tothe filtrate was added 5 g of copper (I) chloride and the mixture wasmagnetically stirred for one day. The now yellow solution was filteredand tetrahydrofuran (THF) was removed under reduced pressure from thefiltrate to leave 10.9 g of pale yellow solid polymer. Spectroscopicanalysis indicated the composition of the solid to have the followingformula:

    [(SiC.sub.6 H.sub.5)H].sub.0.51 [Si(C.sub.6 H.sub.5)].sub.0.49

so that a valency of four is maintained. This polymer was handledbriefly in air as a solid without significant change.

EXAMPLE 2

This example illustrates the preparation of poly(methylhydridosilane)following the procedure outlined in EXAMPLE 1.

To 10 g of a magnetically stirred and mineral oil-free sodium dispersioncovered with 150 ml of THF was added dropwise at room temperature over 2hrs. 20.8 ml of vacuum-transferred methyldichlorosilane (PetrarchSystems, Inc.). The reaction mixture was stirred for four days at about20° C. and filtered in a nitrogen atmosphere. Removal of solvent fromthe filtrate left 4.7 g of pale yellow solid. Spectroscopic analysisindicated the solid corresponded to the composition

    [Si(CH.sub.3)H].sub.0.36 [Si(CH.sub.3)]0.64.

This polymer reacted readily with air, with the formation of Si--Obonds.

EXAMPLE 3

This example illustrates the preparation of a random copolymer of analkylhydridosilane with an arylhydridosilane following the procedureoutlined in EXAMPLE 1.

To a magnetically stirred mixture of 1.61 g of mineral oil-free sodiumdispersion covered with 50 ml of THF was added dropwise over 15 minutesat about 20° C. a solution of 1.73 g of purified methyldichlorosilaneand 2.65 g of purified phenyldichlorosilane in 5 ml of THF. The productwas stirred at about 20° C. for two days and processed according to theprocedure in EXAMPLE 2. Removal of solvent from the filtrate left 1.8 gof pale yellow solid polymer. Spectroscopic analysis indicated the solidcorresponded to the composition:

    [Si(CH.sub.3)H].sub.0.22 [Si(CH.sub.3)].sub.0.4 [Si(C.sub.6 H.sub.5)H].sub.0.37 [Si(C.sub.6 H.sub.5)].sub.0.01.

This polymer was handled briefly in air as a solid, without significantchange.

The copolymer was heated under nitrogen at 10° C. min⁻¹ from ambient to1000° C. Minor weight loss began at 160° C. The main thermogravimetricchange occured in the 240°-480° C. region and was complete by 540° C.Total weight loss was about 50 percent, in contrast to the report byYajima et al. (U.S. Pat. No. 4,283,376) who show a nearly completeweight loss of poly(dimethylsilane) under similar conditions.

EXAMPLE 4

This example illustrates the preparation of poly(hydridosilane)following the procedure outlined in EXAMPLE 1.

Sodium metal (23 g, cut into about twenty pieces) was covered with 600ml of THF and 100 mg of napthalene was added. The green color typical ofsodium naphthalide soon formed. The sodium-containing mixture was cooledby moans of an external liquid nitrogen bath and 27 ml of dichlorosilane(Petrarch Systems Inc., vacuum transferred from 0° C.) was condensedinto the frozen sodium mixture. It was then warmed to -40° C. andmaintained at -40° C. for about four days. The reaction mixture was thenwarmed to ambient temperature and promptly filtered under nitrogen.Removal of solvent from the filtrate left a gummy white solid which wasmixed with 300 ml of toluene to dissolve the polymer. The resultantmixture was filtered and the toluene was removed under vacuum from thefiltrate to leave 0.7 g of a cream colored solid poly(dihydridosilane)whose spectroscopic analyses indicated the presence of a silicon tohydrogen ratio of 1 to 1.9 and confirmed the presence of SiH₂ groups.This polymer reacted readily but not violently with air.

NOTE: Dichlorosilane is a highly reactive gas and may contain SiH₄,which reacts explosively with air. Additionally, storage of thepolysilane --SiH₁.9 --_(n) in the presence of impurities may result indisproportionation and formation of SiH₄. Appropriate precautions shouldtherefore be observed throughout these procedures.

EXAMPLE 5

This example illustrates the preparation of poly(ethylhydridosilane)following the procedure outlined in EXAMPLE 1.

To 10.0 g of sodium (cut into about ten pieces) covered with 250 ml ofTHF, and containing 90 mg of naphthalene, and cooled with an externalliquid nitrogen bath was added by vacuum transfer 10.0 g ofethyldichlorosilane (Petrarch Systems, Inc.). The reaction mixture waswarmed to about 20° C., stirred for 3 days at about that temperature,and filtered in a nitrogen atmosphere. Solvent was removed from thefiltrate under vacuum to yield 2.90 g of pale yellow oil. Spectroscopicanalysis indicated the oil corresponded to the composition

    [Si(C.sub.2 H.sub.5)H].sub.0.79 [Si(C.sub.2 H.sub.5)].sub..21.

This polymer reacted readily with air.

EXAMPLE 6

This example illustrates the preparation of a random copolymer of adialkylsilane and a dihydridosilane following the procedure outlined inEXAMPLE 1.

To a flask containing 11.5 g of sodium (cut into approximately 10pieces), 100 mg of naphthalene, and 250 ml of THF and cooled in liquidnitrogen as in EXAMPLE 4 was added 8.3 ml of purified dichlorosilane and12.1 ml of purified dimethyldichlorosilane (Petrarch Systems Inc.). Themixture was warmed to -40° C. and maintained at that temperature for oneweek. It was then warmed to room temperature, and promptly filtered in anitrogen atmosphere. Removal of solvent from the filtrate gave 2.2 g ofviscous cream-colored oil. Spectroscopic analyses indicated the oilcorresponded to the composition:

    [Si(CH.sub.3).sub.2 ].sub.0.36 [(SiH)(SiH.sub.2)].sub.0.64.

and confirmed the presence of (SiH₂) groups.

This polymer reacted readily with air.

EXAMPLE 7

This example illustrates the preparation of a random copolymer of analkylarylsilane and an arylhydridosilane following the procedureoutlined in EXAMPLE 1.

To a flask containing 4.7 g of sodium (cut into approximately 5 pieces)and 50 ml of THF was added dropwise over 5 min a mixture of 7.3 g ofphenyldichlorosilane and 7.8 g of phenylmethyldichlorosilane (PetrarchSystems, Inc., Bristol, PA) (both silanes were vacuum-distilled beforeuse) at ambient temperature (about 20° C.). The reaction mixture wasstirred for 8 days, and the resultant red solution was filtered toremove excess sodium and NaCl. The deep red filtrate was placed over 7.4g of CuCl, and stirred overnight. The mixture was then filtered toremove excess CuCl, Cu and NaCl, and THF was removed from the filtrateunder vacuum to give 8.0 g of pale yellow polymer. Spectroscopicanalysis indicated the solid corresponded to the composition:

    [Si(C.sub.6 H.sub.5)(CH.sub.3)].sub.0.55 [Si(C.sub.6 H.sub.5)H].sub.0.38 [Si(C.sub.6 H.sub.5 ].sub.0.07

This polymer was handled briefly in air as a solid, without significantchange.

This polymer was further fractionated by the following procedure: 8.0 gof polymer was dissolved in approximately 15 ml of toluene, and addeddropwise to 200 ml of hexanes, with stirring. A white powder formed,which was collected by filtration to give 0.9 g of a white solidpolymer. The solvent was removed from the filtrate to give 6.6 g of verygummy pale yellow polymer.

EXAMPLE 8

This example illustrates the preparation in one step ofpoly(phenylhydridosilane) containing a silyl derivative of sodiumfollowing the procedure outlined in EXAMPLE 1.

To 2.5 g of sodium, cut into approximately five pieces and covered with75 ml of THF, 12.2 g of phenyldichlorosilane was added dropwise overseveral minutes. The reaction mixture was stirred for four days until adeep red solution formed. The reaction mixture was filtered to removeexcess sodium and NaCl, and THF was removed from the filtrate undervacuum to give 7.2 g of deep red solid polymer. Spectroscopic andelemental analyses confirmed the composition of the solid to have thefollowing composition:

    [Si(C.sub.6 H.sub.5)H].sub.0.40 [Si(C.sub.6 H.sub.5)].sub.0.60 [Na].sub.0.17

This polymer reacted readily with air, although it was stable for monthswhen stored as a solid under an inert atmosphere.

EXAMPLE 9

This example illustrates the preparation in one step ofpoly(methylhydridosilane) containing a silyl derivative of sodiumfollowing the procedure outlined in EXAMPLE 1.

To 10 g of sodium covered with 150 ml THF, 23 g of methyldichlorosilanewas added dropwise at ambient temperature over 2 hr. The reactionmixture was stirred for five days at about 20° C. when a deep redsolution had formed. The reaction mixture was filtered through a fineporosity glass frit (4-8 micrometers, dried at 120° C. and placed in aninert atmosphere while hot) to remove excess sodium and NaCl, and THFwas removed from the filtrate under vacuum to give 6.6 g of a deep redsolid polymer. Spectroscopic and elemental analyses confirmed the solidto have the following composition:

    [Si(CH.sub.3)H].sub.0.25 [Si(CH.sub.3)].sub.0.75 [Na].sub.0.10

This polymer reacted readily with air, although it was stable for monthswhen stored as a solid under an inert atmosphere.

EXAMPLE 10

This example illustrates the preparation of a copolymer of analkylarysilane and an arylhydridosilane containing a silyl derivative ofsodium in one step following the procedure outlined in EXAMPLE 1.

To a flask containing 3.7 g of sodium (cut into approximately 4 pieces)and 50 ml of THF was added dropwise over 5 min a mixture of 5.7 g ofphenyldichlorosilane and 6.1 g of phenylmethyldichlorosilane at ambienttemperature (about 20° C.). The reaction mixture was stirred for eightdays, and the resultant red solution was filtered to remove NaCl andexcess sodium. Solvent was removed from the filtrate under vacuum togive 6.2 g of deep red solid. This material was dissolved in 15 ml oftoluene and precipitated into 250 ml of stirred hexanes, to produce 2.3g of bright yellow powder. Subsequent reactions and spectroscopicanalyses indicated the solid corresponded to a composition containing 5mole percent silyl derivative of sodium.

EXAMPLE 11

This example illustrates the preparation of a random copolymer of analkylarylsilane and an arylhydridosilane containing a silyl derivativeof sodium in two steps following the procedure outlined in EXAMPLE 1.

First, 4.6 g of phenyldichlorosilane and 5.0 g ofphenylmethyldichlorosilane were reacted with 3.0 g of sodium (cut intoabout 3 pieces) in 40 ml of THF, filtered, treated with 3.1 g of CuC1and filtered to produce a pale yellow filtrate containing a randomcopolymer of phenylmethylsilane and phenylhydridosilane as in EXAMPLE 7.Second, the solvent was not removed from the polymer, but the filtratewas placed over 1.8 of sodium, and the solution began to turn red withinminutes. The reaction mixture was stirred for approximately 3 hours,then allowed to stand for 20 hours. The reaction mixture was filtered,and solvent removed under vacuum to produce 5.1 g of deep red solidpolymer. This was further treated by dissolution in 15 ml of toluene andprecipitation into well-stirred hexanes (200 ml) to produce 3.3 g ofbright yellow powder. This was collected by filtration and dried undervacuum. Subsequent reactions and spectroscopic analyses indicated thesolid corresponded to a composition containing approximately 8 molepercent silyl derivative of sodium.

EXAMPLE 12

This example illustrates the reaction of a polyhydridosilane containinga silyl derivative of sodium with a compound containing a carbon-halogenbond.

To 135 mg of poly[(phenylmethylsilane)(phenylhydridosilane)] containinga silyl derivative of sodium prepared as in EXAMPLE 10 and dissolved in0.5 ml of benzene-d₆ (Aldrich Chemical Co., Milwaukee, WI) was added 8microliters of benzyl chloride. The red color of the silyl derivative ofsodium disappeared immediately, and spectroscopic analyses indicated thepresence of Si--(CH₂ C₆ H₅) groups in the polymer. In this particularreaction, some deuterium was also incorporated into the polymer.

In a similar reaction using the polyhydridosilane containing silylderivative of sodium (prepared as in EXAMPLE 11) suspended in hexanesand treated with benzyl chloride, Si--(CH₂ C₆ H₅) groups were againformed but no evidence of reaction with solvent was obtained.

EXAMPLE 13

This example illustrates the reaction of a polyhydridosilane with analkene in the presence of a platinum complex known to be hydrosilationcatalyst.

95 mg of poly(phenylhydridosilane) prepared as in EXAMPLE 1 was placedin 300 mg of benzene-d₆ with 180 mg of styrene and 1 mg of H₂ PtCl₆.Within 24 hr of reaction spectroscopic analyses indicated the presenceof SiCH₂ CH₂ (C₆ H₅) groups as well as some unreacted Si--H bonds.

EXAMPLE 14

This example illustrates the reaction of a polyhydridosilane with apolyalkene in the presence of a platinum complex known to be ahydrosilation catalyst to form a highly crosslinked network.

0.31 g of poly(phenylhydridosilane) (prepared as in EXAMPLE 1) wasdissolved in 0.21 g divinylbenzene to form a very viscous mixture. 5microliters of a solution containing 15 weight percent of a platinumcomplex with symmetrical divinyltetramethyldisiloxane was added. Within24 hr of reaction, the sample was very hard and brittle. A controlsample containing no platinum catalyst was still very soft.

EXAMPLE 15

This example illustrates the reaction of a polyhydridosilane with analcohol.

100 mg of poly(phenylhydridosilane) prepared as in EXAMPLE 1 was placedin 1 ml of toluene, and 32 microliters of dry methanol was added. Noreaction occurred. 1 mg of sodium metal was added as catalyst and withinminutes of reaction spectroscopic analyses indicated the presence ofSi--OCH₃ groups, and some unreacted Si--11 bonds.

In another sample, 100 mg of poly(phenylhydridosilane) and 10microliters of dry methanol were placed in 1 ml of THF, and 6 mg of 5weight percent platinum on charcoal was added as catalyst. Within 24 hrof reaction, spectroscopic analyses indicated the presence of Si--OCH₃groups, and some unreacted Si--H bonds.

If a large excess of alcohol is present and under appropriate reactionconditions, Si--Si bond cleavage may also occur.

EXAMPLE 16

This example illustrates the reaction of a polyhydridosilane with anamine.

To a solution of 100 mg of poly(phenylhydridosilane) (prepared as inEXAMPLE 1) in 1 ml of toluene was added 50 microliters ofN-benzylmethylamine. Within minutes of reaction, spectroscopic analysesindicated the presence of Si--N(CH₃)(CH₂ C₆ H₅) groups. Some Si--H bondsremained unreacted.

EXAMPLE 17

In this example a mixture of polyhydridosilane and polyvinyl compoundwere photochemically crosslinked.

150 mg of poly(methylhydridosilane) (prepared as in EXAMPLE 2) wasdissolved in 220 mg of divinylbenzene. The solution was stored at 20° C.in the dark for a week with no change. The sample was then placed underan ultraviolet lamp, and within 15 hr a hard, brittle resin had formed.

EXAMPLE 18

This example illustrates the reaction of polyhydridosilane containing asilyl derivative of sodium with a transition metal halide.

Equivalent amounts of poly(phenylhydridosilane) containing a silylderivative of sodium (prepared as in Example 8) andcyclopentadienylirondicarbonyl bromide were placed in THF. Reaction wasimmediate, and spectroscopic analyses confirmed the presence ofSi--Fe(CO)₂ (C₅ H₅) groups.

EXAMPLE 19

This example illustrates the reaction of a polyhydridosilane with anorganometallic Periodic Group IA compound.

150 mg of poly(phenylhydridosilane) prepared as in EXAMPLE 1 was placedin 1.5 ml of THF. 0.5 ml of 2.5 M n-butyl lithium in hexane (AldrichChemical Co., Milwaukee, WI) was added, and the reaction mixtureimmediately turned orange. Chemical and spectroscopic analyses indicatedthat reaction had occurred at both Si--H and Si--Si bonds, and thatSi--(C₄ H₉) and Si⁻⁻ Li⁺ groups had formed.

EXAMPLE 20

This example illustrates the thermal treatment (pyrolysis) ofpoly(hydridosilane) to pyropolymer.

The poly(hydridosilane) was sensitive to air and all operations withthis polymer were conducted in a nitrogen atmosphere.

Poly(hydridosilane), prepared as described in EXAMPLE 4, and protectedby storage in nitrogen, was dissolved in dry, oxygen-free THF to give asolution (0.1 g of polymer in 1 g of THF). A few drops of this solutionwere placed on a sodium chloride (salt) plate, and the solvent was thenremoved under vacuum to give an adherent film having strong infrared(IR) absorptions. The film (on the salt plate) was placed within alarger, nitrogen-filled infrared cell such as a gas cell to allow an IRspectrum of the film to be obtained. The IR showed absorption bands dueto the Si--H and SiH₂ groups. The film (on the salt plate) was placed ina quartz tube and heated under vacuum at 200° C. for one hour.Thereafter, this plate was allowed to cool, and its IR spectrum wastaken (nitrogen atmosphere). No significant change was noted in the IRspectrum.

After heating of the above film (on the salt plate) at 400° C. for onehour, the absorption bands had almost disappeared and had shifted tolower wavelengths. After heating at 600° C. for one hour, the sample wasblack and infrared absorption bands were no longer visible.

EXAMPLE 21

This example illustrates the pyrolysis of aliphatic,poly(methylhydridosilane) to a pyropolymer.

The conversion of the polysilanes to pyropolymers and ultimate ceramicproducts was monitored by vacuum pyrolysis techniques.Poly(methylhydridosilane) (100 mg, 2.27 mmoles), prepared as in EXAMPLE2, was heated under vacuum at 10° C. min⁻¹ with careful monitoring ofthe volatile products and visual observation of color change. Thenon-condensable gases were removed continuously, collected in a Toeplerpump, and the cumulative total for each 100° C. increment was recordedbefore analysis by mass spectrometry to determine the ratio of CH₄ :H₂(Table I). Volatile compounds condensing in a liquid nitrogen trap wereanalyzed by infrared and mass spectrometry and the final ceramic residue(pyropolymer) was subjected to X-ray, Electron Spectroscopy for ChemicalAnalysis (ESCA), and Scanning Electron Microscopy (SEM) evaluation. By430° C. the polysilane had become bright yellow with production of CH₄(0.04 mmoles), H₂ (0.03 mmoles), and SiH₃ CH₃ (0.29 mmoles). A clearcolorless condensate, which collected just outside the hot zone of thefurnace tube, had an IR spectrum identical to the starting polymer andwas recorded as recovered oligomers and polymers.

                  TABLE I                                                         ______________________________________                                        PYROLYSIS OF POLY(METHYLHYDRIDOSILANE)                                                               Total Gas  Composition                                 Temperature            (mmoles)   (wt %)                                      °C.                                                                              Color        each interval                                                                            CH.sub.4                                                                            H.sub.2                               ______________________________________                                        430       Bright Yellow                                                                              0.067      61    39                                    510       Buff         0.673      42    58                                    600       Blue-black   0.582      10    90                                    700       Lustrous     0.189      12    88                                              grey-black                                                          800       Lustrous     0.163       7    93                                              grey-black                                                          910       Lustrous     0.018      10    90                                              grey-black                                                          ______________________________________                                    

Summarizing, to indicate mass balance in mmoles: ##STR6## The aboveanalysis figures imply that a significant amount of carbon, present asmethyl groups in the starting polysilane, was eliminated as methaneduring the earlier stages of the pyrolysis and that the resultingpyropolymer was likely to be correspondingly richer in silicon.

Although this pyropolymer was found to be largely amorphous, x-rayanalysis showed three diffraction lines attributable to cubic silicon.The C(1s) and Si(2p) photoelectron spectra also revealed that elementalsilicon was present, together with silicon bonded to carbon and acarbide form of carbon. Under the particular reaction conditionsdescribed in this example, more silicon was present as the element thanas silicon carbide.

EXAMPLE 22

This example illustrates the pyrolysis of aromaticpoly(phenylhydridosilane) to a pyropolymer.

The techniques described in EXAMPLE 21, were also used to study thethermal decomposition of polyphenylhydridosilane, prepared as describedin EXAMPLE 1. In this case the volatile products included phenylsilane,benzene and hydrogen. The polymer was again heated under vacuum andbecame bright yellow at 330° C., darkened to amber at 560° C. andfinally converted to a vitreous black ceramic pyropolymer at 910° C.

Summarizing, with amount in mmoles: ##STR7##

The black pyropolymer did not show an x-ray diffraction pattern.Thermolysis of this polymer was also followed thermogravimetrically,using the heating rate and nitrogen flow rate described in EXAMPLE 3.The weight loss curve was broadly similar to that of the copolymer witha maximum weight loss of 48 percent attained by 580° C.

EXAMPLE 23

This example illustrates the pyrolysis of poly(methylhydridosilane) inthe presence of ammonia to form a silicon nitride-containingpyropolymer.

A 0.2 g sample of poly(methylhydridosilane) (see EXAMPLE 2) was heatedunder vacuum to 950° C. at 10° C. per minute, and this final temperaturewas maintained for 5 hrs. There was some loss of volatile products asdescribed in detail in EXAMPLE 21. Without any exposure of the resultantpyropolymer to the atmosphere, an excess of pure gaseous ammonia wasadmitted to the evacuated chamber until a pressure of 10 cm of Hg wasobtained. Heating was continued at 950° C. for 5.5 hours. The resultantpyropolymer was cooled under vacuum and spectroscopic analysis confirmedthe presence of silicon nitride, and its elemental analyses C₂.9 N₁.0Si₃.6 corresponded to a composition 3SiC.Si₃ N₄.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

We claim:
 1. An article comprising a solid polymer having a backboneconsisting essentially of repeating monomeric units having the formula##STR8## wherein R is the same or different and is independentlyselected from the group consisting of (1) hydrogen, (2) a linear,branched, or cyclic aliphatic group having 1 to 10 carbon atoms andoptionally containing at least one Periodic Group VA or VIA atom, (3) anaromatic group which is unsubstitued or substituted by up to three C₁ toC₁₀ linear, branched, or cyclic aliphatic groups, said aromatic oraliphatic groups optically containing at least one Periodic Group VA orVIA atom, the total number of carbon atoms being up to 25, (4) a singlebond connecting two silicon atoms, (5) a metal atom selected from thegroup consisting of Periodic Groups IA and IIA, and (6) an inorgano- andorganometallic group comprising at least one Periodic Group IB and VIIB,VIII, Lanthanide or Actinide element,with the proviso that the ratio ofhydride to silicon is in the range of 0.3 to 2.2; the average number ofmonomeric units of said formula in the polymer is in the range of 20 to4,000, and said polymer being tractable and moisture-sensitive and atleast 0.1 gram of said polymer being soluble in 100 grams oftetrahydrofuran at 20° C.
 2. The article according to claim 1 which is afilm.
 3. The article according to claim 1 which is a fiber.
 4. Thearticle according to claim 1 in which said polymer is a coating.
 5. Thearticle according to claim 1 which is a composite.
 6. The articleaccording to claim 4 which is a photoresist.
 7. The article according toclaim 4 in which said polymer is an adhesive.
 8. The article accordingto claim 1 which is capable of being pyrolyzed to provide a ceramicmaterial or an abrasive.
 9. The article according to claim 1 whereinsaid monomeric units of said polymer are randomly arranged.
 10. Thearticle according to claim 1 wherein in each monomeric unit of saidpolymer R is independently selected from hydrogen, methyl, ethyl,phenyl, and a single bond connecting two silicon atoms.
 11. The articleaccording to claim 1 wherein said polymer is selected from a randomcopolymer of (a) a dialiphaticsilane and a dihydridosilane, and a randomcopolymer of (b) an aliphatichydridosilane and an aromatichydridosilane.12. The article according to claim 1 wherein said polymer comprises atleast one monomeric unit selected from units having the formulae --SiH₂--, --CH₃ SiH--, --C₆ H₅ SiH--, and --C₂ H₅ SiH--.
 13. The articleaccording to claim 1 wherein in said monomeric units of said polymer Ris selected from the group consisting of hydrogen, alkyl, alkoxy,alkylamino, aryl, arylamino, and a single bond connecting two siliconatoms, and combinations thereof.
 14. The article according to claims 1wherein in said monomeric units of said polymer each R is independentlyselected from the group consisting of hydrogen, methyl, ethyl, n-butyl,methoxy, benzyl, benzylmethylamino, phenethyl, and a single bondconnecting two silicon atoms.